The germline genome in hypotrichous ciliates has undergone two profound modifications during evolution: the insertion of noncoding sequences called IESs into most or scrambled configuration. These modifications are eliminated from germline DNA when a germline nucleus (micronucleus) develops into a somatic nucleus (macronucleus) after cell mating. Insertion and removal of IESs, mutation of IES sequence and length, and shifting of position of IESs in genes are to be tracked during evolution by comparing the structure of genes encoding actin I, alpha and beta telomere-binding proteins, and DNA polymerase alpha in 11 hypotrich species spanning a broad range of phylogenetic distance. A mutational model of IES sliding along DNA will be tested by mutagenizing cells with ultraviolet light, ethidium bromide, and methyl nitrosourea and monitoring the positions of IESs in both nonscrambled and scrambled germline genes. Transformation by DNA injection will be used to test the hypothesis that DNA processing in the germline nucleus (micronuleus) during development is guided by DNA sequence information from the old somatic nucleus (macronucleus). The organization of the macronuclear and micronuclear versions of two additional genes, encoding a telomerase subunit and telomerase RNA, will be analyzed in one hypotrich. The experiments deal with the general problem of how an organism can manipulate its own DNA.